Prior to his election to Congress in 2002, Kline was a 25-year veteran of the United States Marine Corps. He retired from the Marine Corps with the rank of Colonel. Kline served as a helicopter pilot in the Vietnam War, commanded all Marine aviation forces in Operation Restore Hope in Somalia, and served as the Program Development Officer at Headquarters Marine Corps, where he was responsible for the Program Objective Memorandum – the document used by the U.S. Armed Services to submit budgetary and planning proposals.

Since he distinguished himself as a helicopter pilot he earned the responsibility of flying Marine One, the President's personal helicopter. Kline was also hand-picked to serve as a personal military aide to President Jimmy Carter, and subsequently to President Ronald Reagan. Mr. Kline's responsibilities during this period included advising the President and our country's senior civilian and military leadership. He was also responsible for carrying the "nuclear football" – the briefcase containing the nuclear war plans and strike options in case of a national emergency.

Among his many medals and awards are four Legion of Merit Medals, a Joint Service Commendation Medal, a Naval Commendation Medal, a Meritorious Service Medal, and the Defense Superior Service Award.